300 REASONING. 



tee for the reality of consciousness, of sensations, of personal 

 existence ; we have no other guarantee for any axiom ; we 

 have no other guarantee for any step in a demonstration. 

 Hence, as being taken for granted in every act of the under- 

 standing, it must be regarded as the Universal Postulate." 

 But as this postulate which we are under an " inexorable 

 necessity" of holding true, is sometimes false ; as " beliefs 

 that once were shown by the inconceivableness of their nega- 

 tions to invariably exist, have since been found untrue," and 

 as " beliefs that now possess this character may some day share 

 the same fate ;" the canon of belief laid down by Mr. Spencer 

 is, that " the most certain conclusion" is that " which involves 

 the postulate the fewest times." Reasoning, therefore, never 

 ought to prevail against one of the immediate beliefs (the 

 belief in Matter, in the outward reality of Extension, Space, 

 and the like), because each of these involves the postulate only 

 once ; while an argument, besides involving it in the premises, 

 involves it again in every step of the ratiocination, no one of 

 the successive acts of inference being recognised as valid ex- 

 cept because we cannot conceive the conclusion not to follow 

 from the premises. 



It will be convenient to take the last part of this argu- 

 ment first. In every reasoning, according to Mr. Spencer, 

 the assumption of the postulate is renewed at every step. At 

 each inference we judge that the conclusion follows from the 

 premises, our sole warrant for that judgment being that we 

 cannot conceive it not to follow. Consequently if the postu- 

 late is fallible, the conclusions of reasoning are more vitiated 

 by that uncertainty than direct intuitions; and the dispro- 

 portion is greater, the more numerous the steps of the 

 argument. 



To test this doctrine, let us first suppose an argument 

 consisting only of a single step, which would be represented 

 by one syllogism. This argument does rest on an assumption, 

 and we have seen in the preceding chapters what the assump- 

 tion is. It is, that whatever has a mark, has what it is a 

 mark of. The evidence of this axiom I shall not consider at 



